Resin particles composed of a radical polymerization product of a vinyl-based monomer are usually produced by a suspension polymerization method, an emulsion polymerization method or the like, and relatively fine particles can be produced. The resulting resin particles are widely used as an additive for coating, an additive for a cosmetic material or the like.
On the other hand, resin particles composed of a polycondensate of a polyester-based resin, a polyamide-based resin, a polycarbonate-based resin, a fluorine-based resin or the like are mainly produced by a mechanical grinding method or a freeze grinding method. It is however known that it is generally difficult to produce fine particles by these methods. As a method for producing fine polyester-based resin particles among resin particles of these polycondensates, the following three methods have been proposed.
First is a method described in Japanese Unexamined Patent Application, First Publication No. Hei 2-215838 (Patent Document 1), and this is a method of obtaining fine polyester-based resin particles of about several micrometers to several tens of micrometers by heating a mixture consisting of a partially crystalline polyester and an intermediate solvent thereof to a melting point of the mixed state or higher, and thereafter, cooling the mixture to a temperature at which solid phase/liquid phase separation is generated.
Second is a method described in Japanese Unexamined Patent Application. First Publication No. 2006-328251 (Patent Document 2), and this is a method of obtaining fine polyester-based resin particles of 0.1 to 50 μm by grinding porous pellets which are obtained by partially depolymerizing a polyester-based resin using glycol.
Third is a method described in Japanese Unexamined Patent Application, First Publication No. Hei 11-114961 (Patent Document 3), and this is a method of obtaining polyester-based resin particles by heat-treating a PET resin as a raw material, thereby bring it into the crystal state where the crystallization degree is 55% or more and an area of a high temperature side second peak region adjacent to a first peak region, which is detected by DSC analysis, has been increased, and thereafter, mechanically grinding the crystal under an ambient temperature.